This invention relates to optical fiber arrays and, in particular, to a hermetically sealed array presenting the cores of the fibers in a sealed planar array. It also includes methods for making such arrays.
One of the major advances in communications in recent years has been the increased use of optical fiber systems for carrying large quantities of information with low distortion and low cost over great distances. Optical systems are also very promising for computing and switching because of the inherently high speeds at which they operate. For these reasons, considerable work has been expended to develop techniques for operating directly on light, without converting the light to electrical energy. The use of such devices will depend to a great extent on the facility with which they can be made.
Optical fibers typically comprise a core of relatively high refractive index glass surrounded by low refractive index glass cladding. The paper, xe2x80x9cAll-Optical Implementation of a 3-D Crossover Switching Network,xe2x80x9d by T. J. Cloonan et al., IEEE Photonics Technology Letters, Vol. 2, No. 6, June 1990, pp. 438-440, describes a free-space photonics switch which takes light from the end of a bundle of optical fibers, performs desired switching functions, and then projects the light into the end of a second array of optical fibers. The optical fiber ends of each bundle form a matrix configuration which must be accurately registered with the other apparatus. Because each fiber core is small (typically about 8 xcexcm), it is important that the ends of each optical fiber bundle be positioned with great accuracy. Fixing the ends of an optic fiber bundle in a desired matrix configuration with the precision needed is difficult and painstaking.
Techniques are now known that can be used to arrange the ends of optical fibers in a desired configuration. See U.S. Pat. No. 5,135,590 issued to applicant Basavanhally et al. on Aug. 4, 1992 and U.S. Pat. No. 5,185,846 issued to Basavanhally et al. on Feb. 9, 1993. These techniques are relatively inexpensive, do not require a great deal of operator skill, and are dependably accurate to within micron or sub-micron dimensions. These techniques involve providing a perforated substrate with a precise array of perforations into which fibers of the bundle are inserted and bonded.
While these techniques have worked well in many applications, in some applications subject to moist environments, water can penetrate the epoxy bonding material and deteriorate the fibers and other optical components of the system.
In accordance with the invention, a hermetic optical fiber array comprises a substrate having a planar surface including an array of perforations for receiving optical fibers, a plurality of fibers having cores disposed in the perforations, the fibers bonded to the substrate with a set of fiber ends substantially coplanar with the surface, and a sealing coating disposed on the planar surface and co-planar ends, the sealing coating covering the substrate/fiber joints but having openings to the cores of fibers in the array.
The fiber array can be bonded within a hollow tubular fiber array housing, and the fiber array housing, in turn, can be adapted to support a microlens in spaced relation to the coplanar arrayed fiber ends and to hermetically attach to an apertured system housing.